SUMMARY In this proposal we request funding to purchase a Leica SP8 STED3X super-resolution microscopy system for the Rutgers New Jersey Medical School (NJMS) imaging core facility. This system will provide the NJMS research community, as well as investigators in other Rutgers schools with state of the art super-resolution imaging capabilities. The imaging system is highly versatile, equipped with a continuous wavelength tunable white excitation laser (470-670 nm), a 405 excitation laser for a commonly used wavelengths not covered by the white laser, and 5 tunable detection channels. Together with the tunable acusto-optical beam-splitter (in place of fixed dichroic mirrors) the system offers unparalleled spectral flexibility for confocal microscopy and STED nanoscopy. The two additional high-power depletion lasers (592 and 775 nm) enable STED imaging and provide high flexibility of fluorophore choice. The system includes optics for shaping the point-spread-function of the excitation light, allowing selection between the higher resolution 2D STED imaging without axial depletion, or 3D STED with axial depletion. The investigators in this shared instrumentation grant used confocal imaging for many years, and their research programs would substantially benefit from this extremely versatile super-resolution microscopy system. Specifically, several investigators study mitochondria in various tissues and disease states, where detecting shape changes and localization of intramitochondrial protein complexes would strongly benefit from the super-resolution Leica STED imaging system. Additionally, several investigators are advancing our understanding of the mechanisms of chronic pain through the imaging of protein dynamics in living neuronal processes and another group seeks to understand the mechanisms of the interaction between immune cells with their target cells. Still another group of investigators study subcellular structures and process, such as telomers, autophagosomes, mRNA processing, transcriptional regulation and extracellular matrix formation where the exceptional resolution of the STED system will provide clear benefits over traditional confocal microscopy. Several investigators intend to image living cells and tissue sections, making the STED system preferable to other super-resolution modalities, such as STORM and SIM. Overall, the Leica STED system would provide investigators at the New Jersey Medical School and the wider Rutgers community with much needed super-resolution imaging capabilities.